Tom Frieden, director of the Centers for Disease Control and Prevention, said Monday that Pham was "clinically stable." Frieden apologized to officials at Texas Health Presbyterian hospital in Dallas. He said his comments Sunday that Pham's infection was the result of a "breach of protocol" did not reflect on Pham or the hospital's efforts. "I apologize if people thought I was criticizing the hospital," Frieden said at a news conference Monday. "And I feel awful that a health care worker became infected while helping an Ebola patient."

A second health care worker who cared for an Ebola patient at a Dallas hospital has contracted the virus herself. The worker, a woman who lives alone, was quickly moved into isolation at Texas Health Presbyterian Hospital, authorities said Wednesday. The news cast further doubt on the hospital's ability to handle Ebola and protect employees. It's the same hospital that initially sent Thomas Eric Duncan home, even though he had a fever and had traveled from West Africa. By the time he returned to the hospital, his symptoms had worsened. He died while being treated by medical staff, including the two women who have now contracted the disease. "I don't think we have a systematic institutional problem," Dr. Daniel Varga, chief clinical officer of Texas Health Resources, told reporters Wednesday, facing questions about the hospital's actions.

It seems like the virus got transmitted in a pretty mundane and unsurprising way- lax containment protocols and improper handling of contaminated gear. I don't think it's suddenly being transmitted in a previously unknown way. The hospital just fucked up.

Here's what actually happened in the 2012 experiment. Six piglets with Ebola were housed next to four monkeys separated in cages. A buffer zone of roughly 8 inches separated the pigs from the monkeys so that they couldn't touch each other directly. Then, two of the monkeys got Ebola fast enough that it was clear that they caught it from the pigs.

But just because this happened between pigs and monkeys doesn't mean it's likely to happen between people. The big difference is that pigs cough and sneeze a lot when they're sick with Ebola — way more than people do.

"You cannot take the pigs and think that it will go the same way in humans," Weingartl said. "One has to consider the species. For pigs, the [Ebola] infection ends up as an infection of the lungs — they have high amounts of the virus in the respiratory tract and so they cough it out. Or when they sneeze or squeal, it just gets out of the lungs. So the virus is in the air directly."

But Ebola affects primates in a different way, Weingartl says. For them, "the main target organ is the liver, so they have high amounts of the virus in the blood and in the feces. They will not be coughing out the virus. And that’s why indirect transmission without contact is probably not happening [among primates and humans]."

Several papers have addressed possible transmission between primates in laboratory settings, including one published on July 25. That one showed no airborne transmission. Another from back in 1995 described transmission without direct contact, but couldn't determine if this was from big droplets, tiny aerosol droplets, or something else.

Of course, it's entirely possible that a big spit droplet from a human Ebola patient could fly a few feet through the air and land on someone else. But current Ebola protection measures seem to guard against this. Health-care workers are told to cover their faces and bodies with protective gear, for example, and patients are generally separated from the general population by a buffer zone of plastic fencing.

What some readers seem to be worried about, though, is not a big cough droplet that travels a few feet, but whether Ebola could travel longer distances in tiny, tiny droplets. This is called "aerosol transmission," and it's something that the measles and some kinds of influenza can do.

Experts say that this is highly unlikely. And this 2012 study of pigs and monkeys doesn't contradict that — indeed, it didn't really address the question of aerosol transmission. It couldn't distinguish between big droplets and little aerosol droplets because the pigs were simply too close to the monkeys.

What the study was designed to do is figure out if Ebola could go from a pig to a primate without them directly touching. Researchers were curious about this because there was evidence that a different, nonlethal-to-humans species of Ebola had done so in the Philippines.

So yes, two monkeys got Ebola from pigs in a laboratory. But that doesn't mean that they would have gotten it if they'd been 10 feet away from each other. And it doesn't mean that any of this would necessarily happen in people

What happens if ebola spreads to South America or Central America? Hundreds of thousands of refugees would flood the USA and the epidemic would spread here killing thousands of Americans; we'd be looking at a 1918 Spanish Flu type of epidemic. I think we need to replace the CDC chief with a type 6 guy; it's better to be overly cautious when the microbe is this deadly.

Senator Rand Paul is alive because of modern medicine and because his attacker punches like a girl.

What happens if ebola spreads to South America or Central America? Hundreds of thousands of refugees would flood the USA and the epidemic would spread here killing thousands of Americans; we'd be looking at a 1918 Spanish Flu type of epidemic. I think we need to replace the CDC chief with a type 6 guy; it's better to be overly cautious when the microbe is this deadly.

Yes, the 1918 flu pandemic was one of the deadliest natural disasters in human history.

Five hundred million were infected and eighty million died across the world.

What happens if ebola spreads to South America or Central America? Hundreds of thousands of refugees would flood the USA and the epidemic would spread here killing thousands of Americans; we'd be looking at a 1918 Spanish Flu type of epidemic. I think we need to replace the CDC chief with a type 6 guy; it's better to be overly cautious when the microbe is this deadly.

What happens if ebola spreads to South America or Central America? Hundreds of thousands of refugees would flood the USA and the epidemic would spread here killing thousands of Americans; we'd be looking at a 1918 Spanish Flu type of epidemic. I think we need to replace the CDC chief with a type 6 guy; it's better to be overly cautious when the microbe is this deadly.